This sounds like you are not aware of the restrictions to all uniqueness techniques for killer. For instance in KSO Weekly 120, one cannot use UR for r12c14, nor any other rectangle with r12c1 because r12c1 are in two different cages and therefore do not form a valid dealy cycle.

I do understand this. I do not have 120 in front of me now but from memory there was a 10 in r1c78 which is 2/8 in some order. 3 rows lower down there is a cage where the c78 squares also turn out to total 10. Uniqueness says that they cannot be 2/8.

It was certainly part of my solving process that r4 c78 could not be 8/2, given r1 c78, and that as a result, at least one of 2 and 8 was elsewhere on r4. If that is what did it for me, why the problem?